Methods for the deposition of thin films of solid state nitrides have been available for many years and are of interest for a variety of reasons. Among the nitrides of the Group III metals, aluminum nitride (AlN) has several potential applications. Its high melting point (2300.degree. C.) and hardness (between Al.sub.2 O.sub.3 and diamond), coupled with its large band gap (6.2 eV) make it a useful ceramic coating particularly for optical or optoelectronic devices. Its piezoelectric nature also renders it valuable for certain other applications. While not as robust as AlN, gallium nitride (GaN) and indium nitride (InN), both of which have the wurtzite structure analogous to AlN, have band gaps of 3.4 and 1.9 eV, respectively, which makes them of interest as semiconductors. There have been several reports describing the interesting properties of mixed compounds such as Al.sub.x Ga.sub.1-x N.
By far the most common source of nitrogen for the preparation of nitrides is N.sub.2 and NH.sub.3. See L. E. Toth, in Transition Method Carbides and Nitrides, Academic Press, NY (1971). Because of the chemical inertness and/or the stability of these two species, high temperatures (1000.degree. C. or greater) are usually required to form the nitride using chemical vapor deposition techniques (CVD). In a CVD process, organometallic precursors are volatilized and then decomposed to yield the metal nitride which is deposited as a film on the target substrate. For example, trimethylaluminum can be decomposed in the presence of ammonia to yield methane and aluminum nitride.
For AlN, lower deposition temperatures have recently been reported using the cyclic trimer, [R.sub.2 AlNH.sub.2 ].sub.3 which is formed by the pyrolysis of the donor-acceptor complex R.sub.3 Al--NH.sub.3. See L. V. Interrante et al., Mats. Res. Soc. Symp. Proc., 73, 359 (1986). The chemical vapor deposition of both AlN and GaN has also been reported using hydrazine as the N-source. See D. K. Gaskill et al., J. Crystal Growth, 77, 418 (1986). Although these approaches have met with some success, a need exists for alternate nitrogen-containing precursors that will permit the use of substantially lower deposition temperatures in the CVD of nitride films.